The East Side CSO Tunnel Project is the largest of all Portland’s projects to greatly reduce the overflows to the Willamette River. When this project is complete in 2011, the volume of combined sewage and stormwater that now overflows to the river when it rains will be reduced by more than 94%. 

The sewer tunnel is 22 feet in diameter and is six miles long. The tunnel route begins at SE 17th and McLoughlin Blvd. and ends on Swan Island where it is connected to the Confluent Shaft.  The tunnel boring machine (TBM) started boring in May 2007 from the Opera Shaft and reached the Port Center Shaft at the Swan Island Pump Station in October 2009.  The TBM reached its southern destination from the Opera Shaft to the McLoughlin Shaft in October 2010.

The Confluent Shaft (from the West Side Big Pipe) and the Port Center Shaft (from the East Side Big Pipe) connects to the Swan Island Pump Station.  The pump station will pump sewage through the Portsmouth Force Main, a pressurized pipe Environmental Services is building as one of the East Side CSO projects.  The force main will discharge to an existing tunnel, which will take the flow to the Columbia Boulevard Wastewater Treatment Plant. 

Project Schedule

¤  February 2003  Design Team Selected - Project Began

¤  July 2004  Preliminary Design - Completed

¤  February 2006  Final Design - Completed

¤  March 2006 Shaft Construction Began

¤   May 2007  Tunnel Excavation Began

¤   October 2009  North Drive Completed

¤   October 2010  South Drive Completed

     December 2011   East Side Big Pipe Completed